| .cas |
Autodesk Cascade License File |
| .cmap |
CmapTools Concept Map File |
| .cleo |
CLEO Grand Theft Auto Mod File |
| .ctv3 |
Citavi 3 Project File |
| .ctv |
Citavi Project |
| .cpk |
DTM Test Log File |
| .cof |
MPLAB COFF File |
| .c3d |
C3D Model File |
| .crf |
Cal3D Binary Materials File |
| .cmf |
Creative Music Format |
| .cnc |
CNC Machine Tool Path |
| .cmod |
Celestia Model |
| .cgr |
CATIA Graphical Representation File |
| .cpf |
Cognos Project File |
| .cat |
Windows Catalog File |
| .ccgame |
XNA Creators Club Game Package |
| .czip |
ZipGenius CryptoZip File |
| .clt |
Clarity Legal Transcript File |
| .cba |
Comic Book ACE Archive |
| .cys |
Cytoscape Session File |
| .cbu |
Comodo Backup File |
| .cbs |
Code Breaker PS2 Save File |
| .cxp |
CX-Programmer Project File |
| .cdo |
Crescendo Music Notation File |